An axial gap permanent magnet motor basically has a structure in which a stator and a rotor are oppositely arranged via a gap in a direction parallel to a rotary shaft, as disclosed in JP Hei 6-38418A and JP2001-57753A. The stator has multiple stator core segments (including teeth) arranged in a circumferential direction of the motor and coils arranged around the stator core segments. The coils are sequentially energized thereby a rotating magnetic field is generated so as to rotate the rotor.
The rotor has a disc-shaped rotor core formed with soft iron or the like, and approximately fan-shaped permanent magnets (field magnets) with their N and S poles arranged alternately along a rotational direction of the rotor on an end surface of the rotor core in the rotary shaft direction.
As the rotor, as disclosed in JP 2005-94955A and JP2008-278649A, there is a well-known rotor in which a soft magnetic material is provided between permanent magnets and/or on the surfaces of the permanent magnets so as to generate reluctance torque. By providing the soft magnetic material for generation of reluctance torque, the reluctance torque, in addition to the magnet torque by the permanent magnet, can be effectively utilized so as to rotate the rotor.
In JP 2005-94955, regarding the soft magnetic material provided between the permanent magnets, disclosed are of a technique (1) of forming the soft magnetic material with laminated magnetic steels being laminated in a direction orthogonal to the rotary shaft (rotor diameter direction) and a technique (2) of forming the soft magnetic material with a powder magnetic core in place of the laminated magnetic steel. Further, a technique (3) of forming the soft magnetic material covering the surface of the permanent magnet with a powder magnetic core is disclosed. Among these soft magnetic materials, the laminated magnetic steel formed in the rotor diameter direction as in the technique (1) can increase the electric resistance in a direction orthogonal to the magnetic flux of the permanent magnet and suppress the eddy current loss. Further, in a case where the soft magnetic material is formed with a powder magnetic core as disclosed in the techniques (2) and (3), since the powder magnetic core is made by mixing metal magnetic powder (e.g. iron powder) with compound resin and by performing compaction molding and heat treating, the electric resistance is high and the eddy current loss can be effectively suppressed.
Further, JP 2005-94955A discloses a technique of forming an entire rotor core including the above-described soft magnetic material with a powder magnetic core and arranging permanent magnets in the rotor core.
JP2008-278649A discloses a rotor structure where a soft magnetic material of a laminated magnetic steel arranged between permanent magnets as described in the technique (1), a soft magnetic material of powder magnetic core covering the surface of the permanent magnets as described in the technique (3) and the permanent magnets (field magnets) are fixed with a nonmagnetic material holder (fixing frame).
The present invention has been made in consideration of the above situation, and provides an axial gap permanent magnet motor having a rotor assembly integrated structure not disclosed in the conventional techniques to ensure strength with respect to a centrifugal force upon rotation of the rotor and suppress flux leakage for efficient driving.